Point of load voltage regulators (VRs) are used to supply microprocessor loads. The microprocessors may have multiple loads (multiple operating voltages). The VRs are step down power converters (e.g., buck converters) that step down the system voltage to the voltage required by the microprocessor load. Systems today often utilize multi-core processors that require individual VRs per core for maximum performance per watt. This has caused a proliferation in the number of VRs used in microprocessor based systems. Therefore, miniaturization of the VRs and proximity to the load are essential to meet area constraints in these systems.
Fabricating the voltage regulators on silicon enables the VR to be miniaturized in close proximity to the load. However, the efficiency range of an on-die buck converter is relatively low (e.g., 77-83%). Furthermore, the buck converters require inductors which call for special additional stages in the silicon fabrication process like sputtering thereby increasing the cost.